This invention relates to flame retardant polyphenylene ether compositions. More particularly, this invention relates to flame retardant thermoplastic polyphenylene ether compositions comprising a thermoplastic polyphenylene ether and a flame retarding amount of the pentate salt of an amino-s-triazine and to a method for rendering thermoplastic polyphenylene ethers flame retardant.
Polyphenylene ethers such as poly-(2,6-dimethyl-1, 4-phenylene) ether are well-known thermoplastic resins having excellent high temperature mechanical properties. These resins, in the native, unplasticized form, are difficult to mold or otherwise melt process, and require the addition of compatable resins such as polystyrene and impact-modified polystyrene to improve the processability and molding properties of the resin for most applications. The preparation and properties of a variety of such blends is disclosed and discussed in U.S. Pat. Nos. 3,883,435 and 4,038,343. Although the addition of styrenic resins to polyphenylene ether resins markedly improves processability, the burning characteristics of such blends are also substantially increased. Thus, though polyphenylene ether resins are generally regarded as non-burning, unfilled blends containing polystyrene or high impact polystyrene have a UL 94 rating of V-1.
The addition of flame retardant additives to blend-modified polyphenylene ether resins will result in blends having a UL 94 rating of V-0, and a variety of halogen-based and phosphorus-based flame retardant additives are known for this purpose. For some applications, however, the use of phosphorus- or halogen-based flame retardant additives may be detrimental to key physical properties and limit the wider use of these blends. An alternative flame retardant would thus broaden the choices available to the resin compounder for meeting the demands of the market.